Linear burners and, in particularly, tubular ribbon burners are commonly used in the area of commercial baking. A typical tubular burner comprises a steel tube with a sealed end and a threaded end for connection to a gas supply, such as an force air or air inspirator for mixing a combustible gas with air.
The burner has a plurality of gas passages or ports disposed along its length.
In earlier burners, the passages or ports were formed by a series of drilling holes along the length of the burner tube.
Many modern burners are of the ribbon type, wherein a plurality of corrugated sheet metal strips are inserted into an elongate opening cut into the burner tube. Ribbon burners are disclosed for instance in U.S. Pat. No. 1,758,628 to Thurm et al., U.S. Pat. No. 2,210,069 to William B. Ensign and U.S. Pat. No. 2,443,101 to John Harold Flynn et al., each of which are incorporated herein by reference.
In a typical ribbon burner, the elongate opening has flat parallel sides and the strips are stacked so as to form an insert which just fits through the opening. To support the insert and keep the various strips aligned, a plurality of pins are inserted at intervals along the length of the tube and transversely through the tube and the plurality of strips. Typically, the pin ends are welded to the tube or casing. FIG. 6 of '628 patent shows the use of a wire wound rod as an insert between plates to provide the burner ports. The wire wound rod is retained in the assembly by transverse pins.
Prior art ribbon burners suffer from a number of disadvantages. The burners are relatively complex and expensive to manufacture and are subject to corrosion and fouling with use. Once the burner tube has been cut to size, threaded at one end and sealed at the other, and the opening has been cut, significant work remains to be done. The ribbon strips must be formed and cut to length and width and holes or slots must be drilled or cut through the strips for subsequent receiving of the transverse pins. Corresponding transverse holes must be drilled through the burner tube.
In a typical ribbon burner, to economize on materials and to maintain adequate gas flow, the insert only slightly penetrates into the central cavity of the burner tube, the holes in the burner tube which receive the pins must be drilled oblique to the tube surface. Such drilling is often difficult and imprecise.
The insert is then assembled from the strips and carefully held in the opening for insertion of the pins. As the opening has parallel sides, the insert may have a tendency to slip, thus requiring care to hold the insert in the proper orientation. The pins having been cut to length are then inserted through the casing and the insert and welded to the casing.
In operation, the thin strips will have a propensity to corrode due to condensation of water of the air used in combustion and the products of combustion and will also tend to become fouled with carbon and other deposits. Forming the ribbons out of a corrosion resistant stainless steel aids but greatly add to the expense. In consequence of using less resistant materials of construction at various intervals the burners must be either replaced or disassembled for replacement of the insert. The latter situation will entail a cumbersome extraction of the pins and a possible forced extraction of the insert, which may have become corroded to or otherwise stuck in the burner opening. The replacement insert will be formed and installed in a similar tedious manner as in the original fabrication.
It is therefore desirable that a burner be designed for ease and low cost of manufacturing, with resistance to fouling and corrosion and more uniform fuel burn characteristics.